If you are willing to use Oxalic Acid (Savogran Wood Bleach from Home Depot is about $8 and is absolutely perfect), then I suggest you do it now. We treated a couple of days ago, and this is a photo of the accelerated mite drop. Basically a nightmare!
Here is a close-up:
We will keep treating every 5 days, until we see less than 25 mites on the slider.